Certain phosphonomethylated amino acids, e.g. glyphosate and its derivatives, are herbicides. Herbicides are useful for controlling or modifying plant growth. Glyphosate and its derivatives are effective in controlling or modifying growth in a wide variety of plant species, including broadleaves, grasses and sedge.
Because glyphosate and its derivatives are so important, new processes for making it and its derivatives faster, cheaper or in greater yields are constantly in demand. A new process for preparing glyphosate from primary amino acids, esters or salts, e.g. glycine ethyl ester, has now been discovered.
When a primary amine is reacted with carbon disulfide and a base, a dithiocarbamic acid salt is formed. This salt can be reacted with dihalomethane to form methylene bisdithiocarbamate. The following reactions are typical: ##STR1##
Such compounds have been used, for example, as fumigants and biocides.